1. Field of the Invention
The present invention relates to a liquid dispenser, and more particularly to a dispenser adapted to attach to an opening of a container, e.g. a can, a barrel, or a bottle, to dispense easily the liquid in the container.
2. Description of the Prior Art
Recently, beer packed in a medium capacity metal or plastic container, e.g. 2 liter and 3 liter container, has begun to be sold. It is desired that a dispenser may be attached to such a container after the closure has been removed in order to dispense the beer easily to a mug or a glass. Many kinds of such dispensers have been proposed. However, the objective of such dispensers has been to solve problems and disadvantages associated with the dispenser itself, such as easy attachment to the container or easy control of pouring quantity. However, such improvements relate only to essential pouring functions.
One pouring problem which often occurs when liquid is poured quickly from a large bottle into a glass is that because of an intermittent liquid flow the liquid overflows the glass. An intermittent liquid flow, which occurs when an unsealed bottle filled with liquid is sharply tilted, is generated in the following stages.
As a first stage, a part of the liquid inside the mouth of the bottle is pushed down and flows out due to the hydrostatic pressure of the liquid because the air pressure inside the bottle is equal to the atmospheric pressure. The flowing out of the liquid increases the volume of the air occupying the space above the liquid in the bottle and lowers its pressure.
As a second stage, when the total pressure on the lower surface of the liquid which is a combination of hydrostatic pressure and the air pressure in the bottle, becomes less than the atmospheric pressure, the liquid flow stops and the air under the lower surface of the liquid enters and rises up as a bubble due to its buoyancy through the liquid to the upper surface. When, by the entering of the air into the bottle, the total pressure on the lower surface of the liquid becomes greater than the atmospheric pressure, a part of the liquid newly occupying the inside of the mouth flows out as in the first stage. Thus, the alternate occurence of the liquid flow stage and the air entry stage generates the intermittent flow.
Many inventions and improvements propose to use an air introduction tube, guiding air from the outside of the container into the air space above the liquid in the container. The air introduction tube makes the liquid flow smoothly because the air is introduced continuously through the tube.